Biogas production in semi-continuous-flow reactors using fresh water hyacinth from the Chao Phraya River

Abstract

Biogas production was studied from the digestion of water hyacinth (WH), co-digestion of WH with cow dung and co-digestion of pre-treated WH with dilute sodium hydroxide (NaOH). The reactors were fed with 20% by fresh weight of the substrate mixture of various ratios in semi-continuous-flow reactors at 30°C. Cow mixed ruminal microorganisms were used as the inoculum. The results indicated that the co-digestion of WH to cow dung to water with a ratio of 10:10:80 was optimal for biogas production. The average methane contents obtained from digestion of WH, co-digestion of WH with cow dung and co-digestion of the pre-treated WH at the recommended ratio were 48.56%, 51.14% and 53.62%, respectively. In co-digestion of WH with cow dung and that of the pre-treated WH at the optimum ratio, the methane yield increased from 144 to 170 L/kg total volatile solids or 115 L to 137 L/kg total solids added in the reactor.